Suspended gate field-effect transistor

Cassidy, J., Pons, S. and Janata, J., Hydrogen response of palladium coated suspended gate field effect transistor, Analytical Chemistry, 58(8), 1757,1986. 

The Kelvin probe inspired the design of another solid-state device called the Suspended Gate Field-Effect Transistor (SGFET) (Blackburn et al., 1983). It resembles the Kelvin probe in that the gate conductor is suspended approximately 1 jU m above the gate insulator, thus forming a gap of a capacitor (Fig. 6.30). 

Fig. 6.30 Schematic diagram of the suspended gate field-effect transistor (SGFET). The selective layer is typically deposited electrochemically...

SGFET suspended gate field effect transistor... 

Josowicz, M., and J. Janata. 1986. Suspended gate field effect transistors modified with polypyrrole as alcohol sensor. Anal Chem 58 514. 

Figure 10.5 Schematic diagram of suspended gate field-effect transistor 1. silicon substrate 2. Si02/Si3N4 insulator 3. metal ridge 4. the gap 5. EP layer Vq and Vp are the applied gate and drain-to-source voltages, respectively.

The chemically selective layer can also be deposited inside a narrow gap formed in the gate structure. Thus, the so-called suspended-gate-field-effect transistor (SGFET) can be produced. Besides Pd [111], layers based on polypyrrole, sensitive to hydrogen-bonding gases [112], can be used, in the same way as polypyrrole-nitrotoluene copolymer, selective to aromatic hydrocarbons [113] and Pb phtalocyanine sensitive to NO2 [114]. Discontinuous or perforated Pd-gate FETs can be used for the determination of NH3 [115] or CO [116]. 

Nieuwenhuizen MS, Harteveld JLN (1994) An automated SAW gas sensor testing system. Sens Actuators A 44 219-229 Oprea A, Weimar U, Simon E, Fleischer M, Frerichs H-P, WUbertz C, Lehmann M (2006) Copper phthalocyanine suspended gate field effect transistors for NOj detection. Sens Actuators B 118 249-254 Ozturk ZZ, Kilinc N, AtillaD, Gurek AG, Ahsen V (2009) Recent studies of chemical sensors based on phthalocytmines. 

Oprea A, Simon E, Fleischer M, Frerichs H-P, Wilbertz C, Lehmann M, Weimar U (2005) Flip-chip suspended gate field effect transistors for ammonia detection. Sens Actuators B 111 582-586 Ostrick B, Mlihlsteff J, Fleischer M, Meixner H, DoU T, Kohl C-D (1999) Adsorbed water as key to room temperature gas sensitive reactions in work function type sensors the carbonate-carbon dioxide system. Sens Actuators B 57 115-119 Ostrick B, Fleischer M, Meixner H, Kohl C-D (2000a) Investigation of the reaction mechanisms, in work function type gas sensors at room temperature by studies of the cross sensitivity to oxygen and water the carbonate-carbon dioxide system. Sens Actuators B 68 197-202... 

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